The winding of assorted plastics and rubbers to make cylindrical articles has long been practiced. Soda straws have been spiral wound, phenolic saturated canvas is wound on mandrels and cured to make bearings, rubber has been saturated into cloth and wound spirally to make industrial hose and in recent years fiberglass saturated with polyesters have been wound into industrial pipe and other shapes.
Polyester fabrications have contributed most of the prior filament winding technology. Polyesters are syrups at room temperature and must be catalized and heated for rapid cure. Syrups are either saturated into fiberglass strands before, during or after winding of same. In all cases the glass is wound against glass because the syrup is too thin to effectively separate a tension wound strand of fibrous glass. Rotation of mandrel or form must be slow when using liquid polyester saturates to avoid centrifugal losses. The alternate method of post-saturation results in pinholes and porosity unless overwrapped with cellophane or equivalent and centrifugally spun to more effectively displace air.
Rotating conveying mandrels using belts, chain or other devices to continuously propel a builtup winding on the mandrel are known. Such require protective continuous overwrapping to prevent fouling of equipment with polyester syrup which effectively destroys the usefulness of the equipment. Such means of conveying and overwrapping layers also prevents efficient heat transfer from mandrel to wound part and thereby prevents such processes from being commercially competitive.
Polyester winding methods also include use of creels rotating about the mandrel. Balancing same at high speeds is impractical because reinforcement packages are not commercially uniform enough to be rotated on a creel at several hundred revolutions per minute.
All objects which can be made by winding have specific strength needs which require great winding pattern flexibility and reliability of pattern once established. Many continuous processes only provide for winding spirals. Pressure pipe and stressed products require that crossed spirals be used and same must usually be balanced.
To present date, to the applicant's knowledge, no thermoset plastic material capable of forming an unreinforced self-supporting strand is known to the trade.
Thermoplastics can form self-supporting strands, yet because of their inherent hot tack and other properties which make guiding and handling of strands difficult, have not been effectively used in filament winding. Because of the kinetic mode of operation needed in working with thermoplastics, an entirely different technique and art is required as compared with reinforced thermoset technology.
In prior commercial art, only one method has been found and it used not guiding or tension control when a rotating tank from mounting on a rail car was slowly moved past the ribbon die of an extruder to slowly produce a heavy overlapped spiral winding.
The technology of thermoplastic filament winding has substantially no background.